PiBot V4.7B — Pin Definition Overview
FluidNC / grblHAL · Plug-in classic ESP32 module · Six external-driver signal groups
FluidNC ports are assigned by the YAML file, so the software functions are configurable rather than permanently fixed.
The definitions on this page match the supplied V4.7B I/O-test YAML. Check your active YAML and board revision before wiring a machine.
The numbered groups on the diagram correspond to the sections below. Click the diagram to view it at full size.
Quick Reference — UART Channels
| Channel | Physical Port | Pins in Test YAML | Typical Use |
|---|---|---|---|
| UART0 | Main USB 12 | On plug-in ESP32 module | Firmware, console and G-code sender |
| UART1 | RS485 3 | TX GPIO.15 · RX GPIO.16 · RTS GPIO.14 | Modbus VFD, 9600 8N1 in test YAML |
| UART2 | RJ12 9 | TX GPIO.25 · RX GPIO.27 when enabled | Compatible PiBot pendant / I/O expander |
Key to the Numbered Groups
💡 Tip: use the pinmap for connector location, the quick-reference tables for signal names, and the full YAML at the bottom of this page for the active test assignment.
Inputs Outputs Power Drivers Interface
1 Eight Input Channels Inputs
Eight signal inputs are available along the board edge. The supplied test YAML assigns them as follows.
| GPIO | Test function | GPIO | Test function |
|---|---|---|---|
| GPIO.2 | Probe, pull-up, active low | GPIO.26 | Tool setter, pull-up, active low |
| GPIO.33 | X limit − | GPIO.32 | X limit + |
| GPIO.35 | Y motor 0 limit | GPIO.34 | Y motor 1 limit |
| GPIO.39 | Z limit | GPIO.36 | A limit |
2 5 V Signal Outputs Outputs
- Header signals: GPIO.12, GPIO.4, GPIO.13 and GPIO.14, with GND.
- Test YAML: GPIO.4 = PWM tool 0, GPIO.12 = laser tool 1, GPIO.13 = 0–10 V generator.
- GPIO.4 and GPIO.12 also drive the matching MOSFET channels in ⑥; they are shared signals, not independent outputs.
3 RS485 Interface
- On-board MAX3485 transceiver with A/B terminal for Modbus RTU devices.
- Test YAML UART1: TX GPIO.15, RX GPIO.16, direction GPIO.14, 9600 baud, 8N1.
- If communication fails, first confirm baud, slave address and A/B polarity.
4 0–10 V Interface Outputs
- Analog output: GPIO.13; use the 0–10 V and GND terminals for the VFD analog input.
- Forward uses GPIO.15 and Reverse uses GPIO.14 with the contact common terminal.
- GPIO.14/15 are shared with RS485. The supplied test YAML leaves Forward/Reverse unassigned while UART1 is enabled.
5 10 V Adjustment Outputs
- Issue the maximum spindle command used by the YAML, then measure the analog output.
- Turn the trimmer slowly until full-scale output reaches the required voltage.
- Do not adjust by guesswork; keep the multimeter connected while calibrating.
6 MOSFET Outputs Outputs
- Two low-side channels:
io.12-MOS-GNDfollows GPIO.12 andio.4-MOS-GNDfollows GPIO.4. - Connect the load between Vmot-main (+) and the corresponding switched MOS-GND terminal.
- Maximum current: 1.5 A per channel. These outputs are for light loads only.
⚠ Do not connect a heavy load directly. Use the MOSFET output to control an external relay or suitable power driver; overloading the channel can burn the MOSFET.
7 Main Power 12–24 V DC Power
- Main carrier-board input: 12–24 V DC.
- Confirm VIN and GND polarity with a multimeter before power-on.
- USB alone powers the ESP32-side connection but is not enough for complete carrier-board testing.
8 OLED Interface Interface
- GND, 3.3 V, SCL GPIO.25, SDA GPIO.27.
- The test YAML enables a 128×64 OLED at I2C address
0x3C. - The OLED shares both signal pins with RJ12 ⑨; enable only one interface at a time.
9 RJ12 Pendant / Expander Interface
- Provides GND, Vmot-main, +5 V and UART2 signals on GPIO.25/GPIO.27 for a compatible PiBot pendant or I/O expander.
- The supplied YAML keeps UART2 commented while the OLED is active.
- Power off before connecting an accessory. Do not assume a telephone cable or third-party pinout is compatible.
⚠ RJ12 and OLED share GPIO.25/GPIO.27 and cannot be enabled at the same time.
10 Six External-Driver Signal Groups Drivers
Each connector provides EN / STP / DIR / GND. All six groups are intended for compatible external stepper drivers; V4.7B has no on-board StepStick sockets.
| Connector | Enable | Step | Direction | Test YAML use |
|---|---|---|---|---|
| X | I2SO.0 | I2SO.2 | I2SO.1 | X motor |
| Y | I2SO.7 | I2SO.5 | I2SO.4 | Y motor 0 |
| Z connector | I2SO.8 | I2SO.10 | I2SO.9 | Y motor 1 |
| A connector | I2SO.15 | I2SO.13 | I2SO.12 | Z motor |
| B connector | I2SO.16 | I2SO.18 | I2SO.17 | A motor |
| C connector | I2SO.23 | I2SO.21 | I2SO.20 | M7 / M8 / M64 P0 signal test |
11 microSD Interface
- SPI MISO GPIO.19, MOSI GPIO.23, SCK GPIO.18.
- Card select: GPIO.5.
- Insert or remove the card only when it is safe to do so and confirm it appears in FluidNC WebUI.
12 Main USB Interface
- The micro-USB connector is on the plug-in classic ESP32 module.
- Use a data-capable cable for FluidNC installation, serial console, boot logs and a USB G-code sender.
- If no serial port appears, try another data cable before troubleshooting the board.
Complete V4.7B Test YAML
📄 The complete test file is displayed below. Click the filename in the code block header to download it. This is an I/O-test profile, not a ready-to-run machine configuration.